diff --git a/src/os_unix.c b/src/os_unix.c
index a39caff..d2f0805 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -2725,9 +2725,8 @@
 }
 
 /*
- * set file permission for 'name' to 'perm'
- *
- * return FAIL for failure, OK otherwise
+ * Set file permission for "name" to "perm".
+ * Return FAIL for failure, OK otherwise.
  */
     int
 mch_setperm(char_u *name, long perm)
@@ -2741,6 +2740,18 @@
 		    (mode_t)perm) == 0 ? OK : FAIL);
 }
 
+#if defined(HAVE_FCHMOD) || defined(PROTO)
+/*
+ * Set file permission for open file "fd" to "perm".
+ * Return FAIL for failure, OK otherwise.
+ */
+    int
+mch_fsetperm(int fd, long perm)
+{
+    return (fchmod(fd, (mode_t)perm) == 0 ? OK : FAIL);
+}
+#endif
+
 #if defined(HAVE_ACL) || defined(PROTO)
 # ifdef HAVE_SYS_ACL_H
 #  include <sys/acl.h>